In standard two-way radio transceivers, all audible signals received by the radio receiver are transmitted out the radio speaker. The transmission of binary digital paging messages on a mixed voice data channel produces unnecessary audible noise on the radio speaker for the holder of the radio, especially in busy systems. With transceivers designed to also receive binary digital paging messages, more paging messages appear within the mixed voice data channel thereby increasing the unnecessary audible noise on the radio speaker.
Through the use of two-way radio transceivers with Private Line (PL) or Digital Private Line (DPL) capability, the unnecessary audible noise can be reduced. PL radio systems send out a low frequency tone for the duration of the message. The frequency of the low frequency tone indicates to the various radio receivers which are to receive the message. A receiver will only key up to receive a message if it is receiving an identified tone. The receiver shuts off when the tone is no longer received. DPL radio systems preface each message with a short burst of digital data to notify which receiver should receiver the message. If the receiver matches the digital data with a digital code stored internally, the receiver will key up and receive the message. At the end of a transmission, the inverse of the digital data code will be sent, shutting off the receiver.
To install PL and DPL capabilities in a radio receiver, extra circuitry must be purchased and installed within the receiver. Further, PL radio systems cannot receive a binary digital paging message because of the restrictions built into the PL systems. Therefore, while PL and DPL radio systems will reduce unnecessary audible noise broadcast through a radio receiver speaker, these systems require additional circuitry and the addition of PL circuitry renders the receiver incapable of receiving a paging message.
Thus, what is needed is a method for enabling the audio output to the radio speaker for nonbinary signals and disabling the audio output to the radio speaker for binary signals while allowing for the reception and decoding of binary digital paging messages.